A stage-type fast scanning calorimetry which can be integrated with other structure characterization approaches

ABSTRACT

A stage-type fast scanning calorimetry which can be integrated with other structure characterization approaches is provided. It relates to the field of phase and microstructure analysis. The stage-type fast scanning calorimetry comprises a sample chamber with reflection window and transmission window, a thermal stage with heating elements and coolant channels inside for temperature controlling and a transmission hole, a temperature control system for sample chamber, a fast calorimetric system. It provides the following advantages. Firstly, the fast calorimetric system is miniaturized in a thermal stage chamber, it allows the integration of fast calorimetry and structure characterization through the reflection, transmission windows and hole. Secondly, the temperature of sample can be compensated in real time by program controlling, in order to stable the sample temperature and study some metastable state conveniently.

TECHNOLOGICAL FIELD

Certain examples of the technology described herein relates to the fieldof phase and microstructure analysis. Specifically, it is a stage-typefast scanning calorimetry which can be integrated with other structurecharacterization approaches, in order to perform in-situ microstructuredetection to the sample after fast heat treatment.

BACKGROUND

Metastable or transient state materials usually exhibit fantasticphysical chemical properties, and many materials with excellentperformance are in special metastable states. For example, we usuallyquench the steels to transit it from austenite to metastable martensite,in order to improve the functional performance Research on metastablematerials have been one of the hotspots, it involves various fieldincluding materials science, physics, chemistry, biology, power,medicine, food, environment, etc. The simplest and most direct way toobtain metastable states is heat treatment. As a result, thermalanalysis, especially fast thermal analysis has been the most effectiveand reliable approach to study metastable materials.

In recent years, Christoph Schick and co-workers built the first fastscanning calorimeter (FSC, Patent Number: US20100046573A1) usingcommercial thin film vacuum sensor (thermal conductivity gauge,TCG-3880, Xensor Integration, NL), the controlled heating and coolingrate was 1 to 10000 K/s (Kelvin per second) or even higher.Specifically, the sample is cut into nanogram to microgram andtransferred onto the film sensor. By which means the thermal capacitiesof the sample and addenda are significantly reduced, so that the heatingand cooling rate could be increased. Using this method, theysuccessfully studied the melting-recrystallizing-remelting processes ofmany polymers such as poly(dimethyl phthalate), polypropylene, polyamideblends, isotactic polystyrene and so on. Under such high heating andcooling rate, some structural transition could be restrained. Fastscanning calorimetry, therefore, can be applied in studying the thermalproperties of some metastable materials. And besides, we can obtain themetastable states by fast heat treatment using FSC. However, theinformation provided only by FSC cannot meet the requirements ofresearch on the structures and properties of metastable materials. As aresults, it is necessary to develop a technique to integrate fastthermal analysis with structure characterization approaches in order toobtain the structural information of sample under metastable states.

There are two difficulties, though, to realize the technique above: 1.The working space of most structure characterization equipment arerelatively small, while the available FSC takes tube-dewar method tocontrol the temperature of sample chamber, which is difficult to in-situintegrate with other equipment. We have to transfer the sample intoother equipment if we want to perform structural characterization of themetastable sample after fast heat treatment. But the structure of thesample has probably changed after this process. 2. As the heatcapacities of the sample and addenda are small for FSC, the illuminationof incoming light will cause great effect to the sample temperature.Unfortunately, the available FSC controls the temperature of sample bypower compensation. Which means, if the effect of light illumination tothe sample temperature exceeds the limit of power compensation, FSC willlose control of the sample temperature and the sample's structure maychange, as well.

SUMMARY

In order to overcome these difficulties, a stage-type fast scanningcalorimetry (ST-FSC) is invented. Besides the FSC's capability, it hasthe following characteristics: 1. There are transmission and reflectionwindows on the opposite sides of the sealed sample chamber, and athermal stage in the chamber containing heating components, pipes forcoolant and a hole for light transmission inside the stage. 2. TheST-FSC can perform fast response and adjustment to the temperaturechange of sample. The way to control the temperature of sample ischanged to fast monitoring it directly by computer program, in order toguarantee the temperature of sample at the setpoint, and prevent theeffect of light illumination from structure characterization equipment.3. The ST-FSC can meet the requirements to detect both transmission andreflection signals, therefore it can be integrated with variousstructure characterization equipment.

A stage-type fast scanning calorimetry is provided. In certain examples,it comprises sample chamber (100), temperature control system (400) ofsample chamber and fast calorimetric system (200).

The sample chamber (100) comprises: a thermal stage (110) with heatingcomponents, pipes for coolant and transmission hole (109) inside,reflection window (107), transmission window (108), wiring terminals(101) for film sensors, signal plug (102) for film sensors, inlet (103)for coolant, outlet (104) for coolant, signal plug (105) for temperaturecontrol of the thermal stage, and atmosphere channel (106). Therefection and transmission windows are on the opposite sides of thesealed sample chamber.

The reflection window (107) allows the incidence light to illuminateonto the sample and the reflected light to exit the chamber.Transmission window (108) allows the incidence light to illuminate ontothe sample through the transmission hole (109), and to exit through thereflection window (107). The selection of reflection window (107) andtransmission window (108)'s transparent materials are according to theapplication, calcium fluoride lenses, for example, are recommended touse in ultraviolet, visible and infrared optical detection, while forthe detection relative to X-ray the polyimide film lenses may be a goodchoice.

The thermal stage (110) provides the ambient temperature for the sample.The surface of the stage is made of silver or other materials with goodheat conduction, in order to keep the temperature uniformity of thesurface. There are temperature sensors, heating elements and pipes forcoolant (like liquid nitrogen or so) inside the thermal stage (110). Theinlet (103) and outlet (104) for the coolant allow the coolant enterinto the inner loop of the thermal stage. The transmission hole (109) isthroughout the thermal stage, facing the reflection (107) andtransmission (108) windows, so that the light can pass though the stageand illuminate onto the sample. The wiring terminals (101) for filmsensors connect the signal wires of the sensors to the signal plug(102). The signal plug (105) for temperature control of the thermalstage connect to temperature control system (400) of sample chamber, inorder to make the temperature of the stage under control. The atmospherechannel (106) allows the atmosphere connection inside and outside of thechamber.

The temperature control system (400) of sample chamber can heat as wellas cool the thermal stage, so that the temperature of stage's surfacecould be hold to a very setpoint.

The fast calorimetric system (200) comprises: reference film sensor(220), film sensor for loading sample (210), fast temperature controland measurement system (300) and computer for program control and dataprocessing (500).

The reference film sensor (220) and film sensor for loading sample (210)should include thermocouples or thermopiles and heating resistance tomeasure and control the temperature. In certain embodiments, thecommercial thermal conductivity gauge model XEN-39391, XEN-39392,XEN-39394, XEN-39395 or so loading on the XEN-014 ceramic substratesfrom Xensor Integration could be used as the sensors.

The fast temperature control and measurement system (300) comprises: PIDcontroller (310) to receive temperature signals from reference filmsensor (220) and produce control signals, differential amplifier (320)to receive temperature signals from both reference sensor (220) andsample sensor (210) in order to produce control signals, and fastdigital-analog converter to output and gathering signals (not marked infigures, integrated with the computer). The controller (310) provides anaverage power for sample sensor (210) and reference sensor (220)according to the received temperature signals. The differentialamplifier (320) provides compensation power for the sample sensor (210)according to the received temperature signals of sample sensor (210) andreference sensor (220). In certain embodiments, the fast digital-analogconverter has 1 digital to analog conversion interface and 8 analog todigital conversion interfaces. And different sampling rate and precisionare adopted to the requirement. In certain embodiments, the samplingrate of asynchronous 1.25 MS/s and accuracy of 16 bit or above arepreferred. Besides, the converter should have appropriate input andoutput buffer to match the sampling rate. According to the heating andcooling rates, the computer (500) write the temperature program intooutput buffer, and provide the signal to the setpoint interface ofcontroller (310) after digital-analog conversion. The measuringinterface of controller (310) is connected to the thermopiles ofreference sensor (220). The controller (310) provides an average heatingpower to both reference sensor (220) and sample sensor (210) accordingto the signals from setpoint and measuring interfaces. In certainembodiments, the differential amplifier (320) is an integratedoperational amplifier circuit of adder or subtractor, also can be a PIDcontroller. It provides compensation power to sample sensor (210)according to the temperature signals from thermopiles of sample sensor(210) and reference sensor (220).

The certain examples described herein could perform thermal analysis atthe heating and cooling rates up to 200,000 K/s. The metastable statesof most samples, especially the polymers, can be captured at thisscanning rates. The ST-FSC can perform in situ spectroscopic detectionto obtain the microstructural information of the sample through thetransmission window (107), reflection window (108) and transmission hole(109), after the metastable states are captured. Meanwhile, thetemperature of sample is stable at the setpoint bymillisecond-time-period program control loop, to prevent the structuraltransition induced by the illumination of light. The above work cannotbe accomplished in other similar equipment (such as the fast scanningcalorimetry described in patent US20100046573A1).

Additional features, aspects, examples and embodiments are described inmore detail below.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is the block diagram of the stage-type fast scanning calorimetry,in which: 100 is the sample chamber, 107 is the reflection windowlocated on the upper surface of sample chamber (100), 108 is thetransmission window located on the lower surface of sample chamber(100), 200 is the fast calorimetric system, 210 is the film sensor forloading samples, 220 is the film sensor for reference, 300 is the fasttemperature control and measurement system, 301 is the cable connectedto film sensors, 400 is the temperature control system controlling thetemperature of thermal stage in the sample chamber, 401 is the signalcable controlling the temperature of sample chamber, 500 is the computer(for program control and data processing, with a digital-analogconverter), 501 is the signal cable between the computer (500) and thetemperature control system (400), 502 is the signal cable between thecomputer (500) and the fast temperature control and measurement system(300).

Additionally in FIG. 1, for the case reflected light is acquired, 610 isthe light source and detector of structure characterization equipmentthat can be integrated with ST-FSC, and 611 is the light path. For thecase transmitted light is acquired, 620 is the light source of structurecharacterization equipment, and 621 is the light path. The lighttransmits from the bottom of sample through the film sensor, andilluminates on the sample. Then the transmitted light is acquired by thedetector (610). It is necessary to note that the light source anddetector (610), light source (620), and light paths (611) and (621) areexcluded from the example described here, they are used for illustratingit only.

FIG. 2 is the profile of the ST-FSC's sample chamber from overhead, theprofile position is shown in FIG. 3 with dash line. In FIG. 2, 100 isthe sample chamber, 110 is the thermal stage in the sample chamber, 101is the terminals for thin film sensors, 102 is the interfaces for thinfilm sensors' signals, 103 is the inlet for coolant, 104 is the outletfor coolant, 105 is the interface for signals controlling thetemperature of thermal stage, 106 is the channel for the atmosphere insample chamber, 210 is the film sensor loading the sample, 214 is theflat cable for sample sensor (210), 220 is the film sensor forreference, 224 is the flat cable for reference sensor (220), 107 is thereflection window. Note that the reflection window (107) here is locatedabove the profile showed in FIG. 2.

FIG. 3 is the profile of the ST-FSC's sample chamber from lateral, theprofile position is shown in FIG. 2 with dash line. In FIG. 3, 100 isthe sample chamber, 101 is the terminals for thin film sensors, 107 isthe reflection window, 108 is the transmission window, 110 is thethermal stage, 109 is the transmission hole throughout the thermalstage, 210 is the sample sensor, 214 is the flat cable for sample sensor(210).

FIG. 4 is a block diagram of the fast temperature control andmeasurement system (300), in which: 110 is the thermal stage, 210 is thesample sensor, 220 is the reference sensor, 310 is the PID controller,320 is a differential amplifier, 211 is the signal wire of thermopilesin sample sensor (210), 212 is the signal wire of average power providedby PID controller (310) to applied on sample sensor (210), 213 is thesignal wire of compensation power provided by the differential amplifier(320), 221 is the signal wire of thermopiles in reference sensor (220),222 is the signal wire of average power provided by PID controller (310)to applied on reference sensor (220).

FIG. 5 is the change temperature of sample when turn on and off theRaman laser illuminated on the sample, and the following adjustment bythe ST-FSC described herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The block diagram of certain embodiments described herein is shown inFIG. 1. The sample sensor (210) and reference sensor (220) are placed onthe surface of thermal stage (110). The ambient temperature of the twosensors (210 and 220) is controlled by the temperature control system ofsample chamber (400). Based on the ambient temperature provided by thethermal stage (110), the fast temperature control and measurement system(300) monitors and controls the temperature of the heating areas in thetwo film sensors (210 and 220) according to the setpoint of temperatureprogram calculated by computer (500). And it returns relative signals tothe computer (500) for further calculation and processing, including thethermodynamic information of the sample.

There are built-in measuring and heating elements in the thermal stage(110). The temperature control system of sample chamber (400) acquiresthe temperature of the thermal stage (110) through the interface (105),and provides heating and cooling signals, accordingly. The heatingsignals applies on the heating elements in thermal stage through theinterface (105), while the cooling signals control the external liquidnitrogen pump or magnetic valve to import the coolant into the thermalstage through inlet (103), and drained from outlet (104) after thecirculation inside the thermal stage. By this means, the temperature ofthermal stage (110) can be controlled by the temperature control system(400). In addition, 106 is a channel to control the atmosphere in thesample chamber in case the atmosphere affects the sample.

Each of the film sensors (210 or 220, shown in FIG. 2) have a heatingarea, and there are heat resistances and thermopiles settled around thearea. The temperature of the heating area can be calculated from thetemperature difference of the heating area (hot junction) and ambienttemperature (cold junction), and the temperature of the thermal stage'ssurface (generally considering, the sensors' ambient temperature isequal to the thermal stage's). The temperature and heating signals areconnected to the wiring terminals (101) by the flat cables (214 and224), and then output from interface (102).

The PID controller (310, shown in FIG. 4) provides average power forboth sample and reference sensors (210 and 220) according to thesetpoint of temperature program and the temperature of the heating areaon the reference sensor (220), while the differential amplifier (320)provides a compensation power for sample sensor (210) according to thetemperature of the heating areas on the sample and reference sensors(210 and 220), so as to maintain the equivalence of the temperaturebetween the heating areas of the two sensors. In the processes above,the temperature on the surface of the thermal stage (110) is hold to aconstant value, which means the cold junctions of the thermopiles in thesensors are constant.

As shown in FIG. 3, the reflection window (107), transmission window(108) and transmission hole (109) are directly facing the heating areaof sample sensor (210). The selection of reflection window (107) andtransmission window (108)'s transparent materials are according to theapplication, calcium fluoride lenses, for example, are recommended touse in ultraviolet, visible and infrared optical detection, while forthe detection relative to X-ray the polyimide film lenses may be a goodchoice. Integrated with spectroscopic equipment, if it is necessary todetect the reflected light, the incident light enters through reflectionwindow (107) and illuminates onto the sample then the reflection lightcould be detected through the same light path. If it is necessary todetect the transmission light, the incident light goes through thetransmission windows (108) and hole (109) and illuminates onto thesample, then the transmission light exits through the reflection window(107).

According to the arrangement shown in FIG. 2 and FIG. 3, the samplechamber (100) can be designed to a size of 170 mm×108 mm×30.34 mm oreven smaller. Therefore, the ST-FSC can be conveniently and effectivelyintegrated with various microstructure characterization equipment,including optical microscopy, micro-Raman spectroscopy and X-rayscattering, etc.

In order to avoid the incident light affecting the temperature ofsample, the computer (500) detects the sample temperature in real time,which can be calculated from the signals obtained by fast temperaturecontrol and measurement system (300). And meanwhile, the temperature ofsample is stable at the setpoint by millisecond-time-period programcontrol loop. An experiment was performed to verify effect of thismethod. A small piece of polyethylene terephthalate was taken as sample,and illuminated by a laser source with a power of 6 mW and wavelength of785 nm. The temperature of sample was detected during turning on and offthe laser source, as shown in FIG. 5. The result reveals that thefluctuation of temperature is controlled in ±0.8 K, and the adjustingtime is within 0.6 s.

In addition, in order to ensure the reliability of results when theST-FSC is integrated with microstructure characterization equipment, thefollowing experimental scheme is suggested. First, to obtain the desiredstate of samples by thermal treatment of ST-FSC using a specifictemperature program. Second, to quench the sample to the temperature farbelow the one that may induce the structural transition of the sampleand hold, the cooling rate should be high enough to suppress anystructural transition. Third, to characterize the samples structure bythe integrated equipment.

The detailed description above is not the limitations, but only used toillustrate a certain example of this invention. Ordinary technicists inrelative technical fields can also make various changes under thisdescription. So all the equivalent technical proposals also belong tothe scope of the invention.

What is claimed is:
 1. A stage-type fast scanning calorimetrycomprising: a sample chamber (100) with reflection window (107) andtransmission window (108); a thermal stage (110) with heating elementsand coolant channels inside for temperature controlling, and atransmission hole (109) through the stage; a temperature control systemfor sample chamber (400); a fast calorimetric system (200).
 2. Thestage-type fast scanning calorimetry of claim 1, in which the samplechamber comprises: thermal stage with a transmission hole (109),reflection window (107), transmission window (108), wiring terminals(101) for thin film sensors, signal plug (102) for thin film sensors,coolant inlet (103), coolant outlet (104), signal plug (105) fortemperature control of the thermal stage, atmosphere channel (106). Thereflection window and transmission window are located on the twoopposite sides of the chamber.
 3. The stage-type fast scanningcalorimetry of claim 1, in which the temperature control system forsample chamber (400) can heat as well as cool the thermal stage, so thatthe temperature of stage's surface could be hold to a very setpoint. 4.The stage-type fast scanning calorimetry of claim 1, in which the fastcalorimetric system (200) comprises: a thin film reference sensor (220),a thin film sample sensor (210), a fast temperature control andmeasurement system (300) and a computer for program control and dataprocessing (500).
 5. The stage-type fast scanning calorimetry of claim2, in which the thermal stage (110) provides ambient temperature for thesample, the surface of the stage is made of silver or other materialswith good heat conduction, in order to keep the temperature uniformityof the surface. The thermal stage (110) is with temperature sensors,heating elements and channels for coolant. The coolant inlet (103) andoutlet (104) are used to circulate the coolant inside the stage. Thetransmission hole (109) is throughout the thermal stage, facing thereflection (107) and transmission (108) windows, so that the light canpass though the stage and illuminate onto the sample. The wiringterminals (101) for film sensors connect the signal wires of the sensorsto the signal plug (102). The signal plug (105) for temperature controlof the thermal stage connect to temperature control system (400) ofsample chamber, in order to make the temperature of the stage undercontrol. The atmosphere channel (106) allows the atmosphere connectioninside and outside of the chamber.
 6. The stage-type fast scanningcalorimetry of claim 4, in which the thin film reference sensor (220)and sample sensor (210) should include thermocouples or thermopiles andheating resistance to measure and control the temperature.
 7. Thestage-type fast scanning calorimetry of claim 4, in which the fasttemperature control and measurement system (300) comprises: PIDcontroller (310) to receive temperature signals from reference filmsensor (220) and produce control signals, differential amplifier (320)to receive temperature signals from both reference sensor (220) andsample sensor (210) in order to produce control signals, and fastdigital-analog converter to output and gathering signals.